Direct visualization of flow-induced conformational transitions of single actin filaments in entangled solutions

While semi-flexible polymers and fibres are an important class of material due to their rich mechanical properties, it remains unclear how these properties relate to the microscopic conformation of the polymers. Actin filaments constitute an ideal model polymer system due to their micron-sized lengt...

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Bibliographic Details
Published in:Nature communications 2014-10, Vol.5 (1), p.5060-5060, Article 5060
Main Authors: Kirchenbuechler, Inka, Guu, Donald, Kurniawan, Nicholas A., Koenderink, Gijsje H., Lettinga, M. Paul
Format: Article
Language:English
Subjects:
14/19
631/57/2272/2273
639/301/54
639/766/189
Actin Cytoskeleton - ultrastructure
Humanities and Social Sciences
Mechanical Phenomena
Microscopy, Confocal
multidisciplinary
Polymers
Science
Solutions
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Summary:While semi-flexible polymers and fibres are an important class of material due to their rich mechanical properties, it remains unclear how these properties relate to the microscopic conformation of the polymers. Actin filaments constitute an ideal model polymer system due to their micron-sized length and relatively high stiffness that allow imaging at the single filament level. Here we study the effect of entanglements on the conformational dynamics of actin filaments in shear flow. We directly measure the full three-dimensional conformation of single actin filaments, using confocal microscopy in combination with a counter-rotating cone-plate shear cell. We show that initially entangled filaments form disentangled orientationally ordered hairpins, confined in the flow-vorticity plane. In addition, shear flow causes stretching and shear alignment of the hairpin tails, while the filament length distribution remains unchanged. These observations explain the strain-softening and shear-thinning behaviour of entangled F-actin solutions, which aids the understanding of the flow behaviour of complex fluids containing semi-flexible polymers. Semi-flexible polymers are an important structural building block in living cells, which possess unique mechanical properties. Here, the authors visualize the shear-induced conformational transition of actin filaments as a model system to study cell formation in cytoplasmic flows.
ISSN:2041-1723
2041-1723
DOI:10.1038/ncomms6060